Sensitive electro-magnetic tripping device of the re-setting type



April 29,1969 ALLETRU 3,441,883 1 SENSITIVE ELECTROMAGNETIC TRIPPING DEVICE OF THE RE-SET'I'ING TYPE Sheet Filed Mgrch 17. 1967 DEVICE OF THE HIS- SETTING TYPE Sheet 3 012 Filed March 17, 1967 v Q @VWI REE TQE

United States Patent 3,441,883 SENSITIVE ELECTRO-MAGNETIC TRIPPING DEVICE OF THE RE-SETTING TYPE Jean Alletru, Villemomble, France, assignor to LIndustrie Electrique de la Seine, Romainville, France Filed Mar. 17, 1967, Ser. No. 623,909 Claims priority, application France, Mar. 22, 1966,

Int. Cl. H01f 3 /12, 7/00, 7/08 US. Cl. 335234 7 Claims ABSTRACT OF THE DISCLOSURE A sensitive electro-magnetic tripping device of the resetting type, comprising a magnetic circuit with three branches containing respectively a permanent magnet, a magnetic shunt and an operating coil, and a magnetic vane acting as a balance bridge on the second branch, and a spherical cap terminating the third branch, a first series air-gap being formed between the operating coil and the vane, this first air-gap being formed between the spherical cap and the vane, a circular cylinder terminating the second branch and a second series air-gap being 'formed between the magnetic shunt and the vane, this second air-gap being formed between the circular cylinder and the vane, and two guides holding the vane bi-laterally on the circular cylinder with a pre-determined play which is equal on both sides.

The invention relates to a tripping device of the type applying the known principle of reduction of magnetic flux in a moving system so as to cause the pulling-off of that system.

French Patent No. 1,145,282 of the Vapor Heating Corporation which originates from the US. Patent No. 2,844,684 to W. W. Anderson and D. J. Hammerand describes for example an electro-magnetic contactor with a single stable position, comprising a magnetic circuit with three branches, one branch having a permanent magnet, the central branch having a magnetic shunt, the third branch having an electro-magnet, and, disposed like a balance bridge on the central branch, a magnetic vane normally attracted by the permanent magnet from which it is pulled away by the electro-magnet.

The invention has as an object the provision of a tripping device (an apparatus with two stable positions) having a construction similar to that described above, which offers simultaneously the following advantages:

Its rated characteristics are readily reproducible; Its fidelity is excellent;

Its sensitivity is excellent;

It is easy to manufacture by mass production;

Its production cost is low.

In brief, the tripping device according to the invention is characterized by the addition of a series air-gap between the moving vane and the electro-magnet branch, by the particular shape of the said air-gap, which is formed between a spherical cap and a plane face, by the addition of a series air-gap between the moving vane and the permanent-magnet branch, by the special form of this air-gap which is formed between a circular cylinder and a plane surface, and by the structure of the vane, which first pivots without friction for a pre-determined portion of its pulling-away travel. A fixed cylindrical shaft terminates the central branch of the magnetic circuit, and the vane is held bi-laterally on this shaft by two guides, with a pre-determined play which is equal on both sides.

It will be noted that the flat vane, the spherical cap and the cylindrical shaft are standard machine par-ts and therefore these two air-gaps are easy to reproduce at a low production cost. It will also be observed that the rolling of the vane without slip on the cylindrical shaft during the first portion of its pulling-away travel is effected without friction and gives the tripping device excellent sensitivity and high fidelity. It should also be noted that the rolling with slip of the vane on the cylindrical shaft during the second part of its release travel, effected with friction of the vane on this shaft, ensures a self-cleaning effect of this air-gap. It will be seen later that the same self-cleaning action of the two air-gaps is produced during the second portion of the re-engagement travel of the vane during re-setting of the tripping device, and this self-cleaning of the two air-gaps is essential to the high degree of fidelity of the tripping device according to the invention.

The invention will be described with reference to the accompanying drawings, given by way of non-limitative examples, in which:

FIG. 1 shows the magnetic diagram of a tripping device in accordance with the invention;

FIGS. 2 and 3 are general diagrammatic sections, longitudinal and transverse, of a tripping device according to the invention;

FIGS. 4 to 8 are details explaining the above rolling movements, without slip and with slip, of the vane of a trippig device according to the invention;

FIG. 9 is a perspective exploded view of a tripping device in accordance with the invention;

FIG. 10 is a detail, showing a tripping device with increased sensitivity, according to the invention;

FIG. 11 is similar to FIG. 2, and shows a tripping device which provides a greater tripping force, according to the invention; and

FIG. 12 is similar to FIG. 2, and shows a further tripping device according to the invention, without opposing spring.

Referring now to FIG. 1, the tripping device accord ing to the invention comprises:

A magnetic circuit 1 with three branches;

In one branch, a permanent magnet 2 with a series air- In the central or second branch, a magnetic shunt 4, which shunts a substantial portion of the magnetic flux produced by the permanent magnet 2;

In the third branch, through which passes the other portion of the magnetic flux produced by the permanent magnet 2, an electric operating coil 5 which can produce a flux when given an appropriate electric excitation; and bridged across the second and third branches, a moving system 6 in series with two airgaps 7 and 8 and subjected to a mechanical releasing force F.

In normal service, the coil 5 is not excited and the moving system 6 is held attracted by the flux in spite of the mechanical force F. The release is obtained by exciting the coil 5, which produces a flux reducing the flux sufficiently for the moving system 6 to be released by the action of the mechanical force P which has become preponderant.

With reference to FIGS. 2 and 3, the magnetic circuit comprises a base 11 of magnetic material, with a return square 12 which constitutes the magnetic shunt, the reluctance of which is determined by a cut-away portion 13. The permanent magnet 15 is fixed on the base 11, for example by welding. On the return square 12 and above the permanent magnet 15, the cylindrical shaft 17 is fixed parallel to the base 11, for example, by riveting at 16; the fiat vane 19 rolls on the said shaft.

On the base 11, the core 22 of the operating coil 23 is fixed perpendicularly, for example, by riveting at 21;

this core 22 is terminated by a spherical cap 25, to which the fiat vane 19 is attracted. The mechanical force F for the release is applied to the vane 19 opposite to the cap 25 with reference to the cylindrical shaft 17. Means are provided (described below with reference to FIGS. 4 to 8 and following) for guiding the Vane 19 and permitting it to roll on the cylindrical shaft 17 as it releases.

From the above it is clear that the tripping device according to the invention has two stable positions: the position of attraction or engagement shown in FIGS. 2 and 3, and the position of release, the vane 19 being moved away from the spherical cap until it comes into contact with a mechanical abutment (not shown) simultaneously by the mechanical force F and by the reduction of the air-gap between the upper pole of the permanent magnet 15 and the left-hand, downwardly-moved portion of the vane 19. The change from one position to the other will be described with reference to the details given in FIGS. 4 to 8. There is again found the fixed cylindrical shaft 17 having its center and radius R, the vane 19 and the permanent magnet 15; the vane 19 is provided with two perpendicular guiding members 27 and 28, enclosing the cylindrical shaft 17 with a play I having the same value J on both sides of the vane.

FIG. 4 shows the vane 19 in the engaged position; it bears against the generator line A of the cylinder 17 and, as will be shown later, the play I is located wholly on the left-hand side, between the guiding member 27 and the cylinder 17. When the vane 19 is released under the action of the coil, the vane is actuated by the force F and rolls, first without sliding on the cylinder 17 until the play J has wholly passed to the right-hand side between the guiding member 28 and the cylinder 17 (see FIG. 5). The vane has then pivoted through an angle a:

a=A6B=% (in radians) Then, as the force F continues to act, the vane 19 continues to roll but by sliding, on the cylinder 17 (FIG. 6) through an angle [3:

the play I remains wholly located on the right-hand side between the guiding member 28 and the cylinder 17.

When re-setting, by the action of the re-setting force R which is applied on the right-hand side on the vane 19, there is first a rolling movement Without slip (FIG. 7) through an angle COD equal to the above angle a, the play I returning to the left between the guiding member 27 and the cylinder 17; there is then a rolling movement with slip (FIG. 8) through an angle DOA equal to the above angle ,8, the play I remaining on the left between the guiding member 27 and the cylinder 17, which is justified by FIG. 5 and the initial location of the play I.

It will be observed that, as already stated, the first part of the release travel (FIG. 4 to FIG. 5, angle a) is effected without friction, which results in the excellent sensitivity of the tripping device according to the invention. The second part of the release travel (FIGS. 5 to 6, angle 5), and the second part of the re-setting travel (FIGS. 7 to 8, angle ,3), are effected with slip of the vane 19 on the cylinder 17, thus producing a self-cleaning action of the two air-gaps, as necessary to retain the excellent fidelity of the tripping device according to the invention.

By way of indication, the applicants have obtained good results with an angle a of the order of 2 degrees, and an angle 13 of the order of 7 degrees.

FIG. 9 shows in exploded perspective view a construction of the tripping device described above. The same parts are shown in this figure with the same reference numbers. In addition, the cylindrical shaft 17 is riveted at its portion 16 into a bore 31 formed in the square 12, and it comprises at its other extremity a circular groove 32. The core 22 is riveted at its part 21 in a bore 33 in the base 11.

In order to give an elastic nature to the mechanical coupling of the vane to the external tripping-resetting chain, the vane 19 co-operates with a spring which is fixed to it by an eyelet passing into the bores 41 and 42; this spring 40 is shaped longitudinally in a double bend to form a raised fiat portion 43 which is the coupling member and with the said external chain. At the other extremity, a bored hole 45 serves as the point of attachment of a tension spring 46, the other attachment point of which is an adjustment screw 47 located in a passage 48 of the base 11. It is this spring 46 which applies the force F on the vane 19.

Transversely, the spring 40 is U-shaped; one of the arms of the U is cut-out to form, for one side of the vane 19, the guides 27 and 28 already described; for the other side of the vane 19, the other arm of the U is cut-out in a round window 50, larger than the diameter 2R of the cylinder 17, and extended by a slot forming two guides 27 and 28, and separated by a distance greater than the diameter of the circular groove 32 of the cylinder 17 by the same play I which is provided between the guides 27, 28 and the cylinder 17. This achieves the desired guiding of the vane 17 and its pivotal movement while remaining parallel to itself. I

Purely by way of indication of the possible sensitivity, the applicants have obtained an operation of the tripping device with an operating power, on alternating the current, of the order of 5,000 micro-v.a.

The tripping device according to the invention lends itself to a large number of alternative forms.

It may for example be desired to increase its sensitivity. FIG. 10 shows a modification designed to that end. The core 22 is terminated by a flat disc 61, against which the vane 19 abuts by an impression or a small punched-out rounded boss 62; the reluctance of the airgap between the vane and the core is thus reduced.

As a further example, it may be desired to increase the mechanical force liberated by the tripping device when the vane is released. FIG. 11 shows a modification adapted to this purpose. A stop-member 71 of magnetic material is fixed on the base 11 on the side opposite to the coil 23. Upon release of the vane, the reduction of the air-gap between the stop 71 and the vane 19 produces a reinforced attraction of this latter by the permanent magnet (15.

As a further example, the spring 46 may be dispensed with; the force F required for pulling-off the vane 19 is then supplied by the permanent magnet 15 which is located, as shown in FIG. 12, on the base 11 on the side of the shaft 17 opposite to the coil 23, in a position which may be fixed or adjustable.

What I claim is:

1. A sensitive electro-magnetic tripping device of the re-setting type, comprising a magnetic circuit including three branches of which one is a central branch, a permanent magnet in one of said branches, a magnetic shunt in the central branch, an operating coil in the third of said branches, and a magnetic vane acting as a balance bridge on the second branch, a spherical cap terminating said third branch, there being provided a first series airgap between the operating coil and the magnetic vane, said first air-gap being formed between said spherical cap and said vane, a circular cylinder terminating the second branch, there being provided a second series air-gap between the magnetic shunt and the magnetic vane, said second air-gap being formed between said circular cylinder and said vane, and two guides holding the vane bilaterally on the circular cylinder with a play which is equal on both sides.

2. A sensitive electro-magnetic tripping device of the re-setting type, comprising a magnetic circuit including three branches of which one is a central branch, a permanent magnet in one of said branches, a magnetic shunt in the central branch, an operating coil in the third of said branches, and a magnetic vane acting like a balance bridge on the second branch, a flat disc terminating said third branch, a punched-out boss on said vane, there being provided a first series air-gap between the operating coil and the magnetic vane, said first air-gap being formed between said flat disc and said rounded boss on the vane, a circular cylinder terminating said second branch, there being provided a second series air-gap between the magnetic shunt and the magnetic vane, said second air-gap being formed between said circular cylinder and said vane, and two guides holding the vane bi-laterally on the circular cylinder with a play equal on both sides.

3. A tripping device as claimed in claim 2, in which said magnetic circuit comprises a base, a return square extending from said base and including a cut-away portion, the permanent magnet being fixed on the base and the cylinder being fixed on the square above said permanent magnet.

4. A tripping device as claimed in claim 3, and further comprising an external tripping-resetting chain, a spring fixed on said vane, and adapted for forming a connection with the external tripping-resetting chain, and constituting said guides, on one side by a rectangular opening and on the other side by a round window extended by a rectangular slot cooperating with a circular groove in said cylindrical shaft.

5. A tripping device as claimed in claim 3, comprising an abutment of magnetic material, fixed on said base on the opposite side to the operating coil, underneath said vane.

6. A tripping device as claimed in claim 3, in which the permanent magnet is mounted on the base, on the side opposite to the operating coil, underneath the vane.

7. A tripping device as claimed in claim 6, in which said permanent magnet is mounted on the base in an adjustable position.

References Cited UNITED STATES PATENTS 2,832,921 4/1958 Horman 335-269 XR 2,891,199 6/1959 Ugon 335269 3,109,126 10/1963 Hailes 335234 3,125,652 3/1964 Richert 335-179 BERNARD A. GILHEANY, Primary Examiner.

D. M. MORGAN, Assistant Examiner.

U.S. Cl. X.R. 335-179, 236 

